Polycarbonate resin has been used as an engineering plastic due to its excellent impact strength, self-extinguishing properties, dimensional stability and heat resistance as compared to other resins. Therefore, polycarbonate resin has been widely used in the production of office automation (OA) instruments, electric or electronic goods and the like.
Polycarbonate resin, however, can have poor flowability due to its high melting point and thus can require high processing temperatures. High processing temperatures can be problematic because the impact resistance of the resultant molded product can deteriorate. For this reason, polycarbonate resin can be blended with various impact modifiers to improve impact resistance.
Although these impact modifiers can improve impact strength of the polycarbonate resin, the use of such impact modifiers can cause other problems. For example, a butadiene rubber-based impact modifier commonly used in polycarbonate tends to degrade or scorch during molding at temperatures greater than 300° C., which can deteriorate heat stability and weather resistance and limit the uses of the resin. An acrylate rubber-based impact modifier may provide good heat stability and weather resistance, but the coloration property and impact resistance at low temperatures can be poor.
U.S. Pat. Nos. 4,994,522 and 5,132,359 are directed to silicone impact modifiers for vinyl chloride resins. However, when these impact modifiers are used in polycarbonate resin, the coloration property still deteriorates.